Heterotic loci analysis for root traits of maize seedlings using an SSSL test population under different nitrogen conditions

Exploitation of heterosis is an efficient strategy to increase crop production, improve quality, and enhance resistance to biotic and abiotic stresses. However, heterosis shows significant genetic × environment effects. Nitrogen is an important nutrient that affects crop development and grain yield. Hybrid maize performs significantly and differently depending on the nitrogen conditions, but the genetic basis of maize heterosis under different nitrogen conditions is unclear. In this study, a test population comprising a set of single segment substitution lines (SSSLs) was used to identify heterotic loci (HL) for root-related traits of maize seedlings under two nitrogen conditions. We identified 80 HL for the root system and related traits in maize seedlings, consisting of 16, 18, 10, 11, 11, and 14 HL associated with root length (RL), root surface area (RSA), root average diameter (RAD), shoot dry weight (SDW), root dry weight (RDW), and plant height (PH), respectively. Among them, 13% of the HL were detected under both nitrogen conditions simultaneously, including the HLs hRL1b , hRL7 , hRL9 , hRSA7a , hRSA9a , hRAD1a , hSDW6 , hSDW7a , hSDW7b , and hPH6a , but most of the HLs (87%) were not detected under both nitrogen conditions. The results indicated that, in maize, heterosis also exists in the interaction between genotype and nitrogen level.